The recent rise in oil prices has resulted in extreme competition among global automakers for improving fuel efficiency. For an engine, the automakers are making an effort to reduce the weight of the engine and improve fuel efficiency thereof by a downsizing technology or the like. Meanwhile, fuel efficiency improvements methods, for example using a transmission mounted in a vehicle, include a method for allowing an engine to be operated at a more efficient operation point through multi-staging of a transmission to ultimately improve fuel efficiency. Further, the multi-staging of the transmission, as described above, enables an engine to be operated at a relatively low revolutions per minute (RPM) band, thereby substantially reducing the noise of a vehicle.
However, as the number of gear-shifting stages of a transmission increases, the number of internal components included in the transmission increases and thus the mountability, production costs, weight, and transmission efficiency of the transmission decrease. Therefore, to maximize a fuel efficiency improvement effect through the multi-staging of the transmission, it may be important to design a transmission structure capable of deriving maximum efficiency by using a minimal number of components and a comparatively simplified configuration.
The above information disclosed in this section is merely for enhancement of understanding of the background of the present disclosure and should not be taken as acknowledgement that this information forms the prior art that is already known to a person skilled in the art.